diff --git a/webapp/graphite/render/functions.py b/webapp/graphite/render/functions.py
index 8630feb8f..329149ff9 100644
--- a/webapp/graphite/render/functions.py
+++ b/webapp/graphite/render/functions.py
@@ -2427,6 +2427,9 @@ def nonNegativeDerivative(requestContext, seriesList, maxValue=None, minValue=No
 
 
 def _nonNegativeDelta(val, prev, maxValue, minValue):
+  if val is None:
+    return None, None
+
   # ignore values larger than maxValue
   if maxValue is not None and val > maxValue:
     return None, None
@@ -2434,7 +2437,7 @@ def _nonNegativeDelta(val, prev, maxValue, minValue):
     return None, None
 
   # first reading
-  if None in (prev, val):
+  if prev is None:
     return None, val
 
   # counter increased, use the difference
diff --git a/webapp/tests/test_functions.py b/webapp/tests/test_functions.py
index cf3fce468..56f7dd959 100644
--- a/webapp/tests/test_functions.py
+++ b/webapp/tests/test_functions.py
@@ -1798,6 +1798,10 @@ def test_perSecond_nones(self):
         result = functions.scaleToSeconds({}, functions.nonNegativeDerivative({}, seriesList), 1)
         self.assertEqual(list(expected[0]), list(result[0]))
 
+        # None values should not raise TypeError when maxValue is set
+        result = functions.perSecond({}, seriesList, maxValue=1000)
+        self.assertEqual(list(expected[0]), list(result[0]))
+
     def test_perSecond_max(self):
         seriesList = self._gen_series_list_with_data(key='test',start=0,end=600,step=60,data=[0, 120, 240, 480, 960, 900, 120, 240, 119, 479])
         expected = [TimeSeries('perSecond(test)', 0, 600, 60, [None, 2, 2, 4, None, None, None, 2, 6, 6])]